Jupiter is hit by an average of 6.5 objects per year that create
impacts large enough to be visible from Earth, according to preliminary
results from a worldwide campaign by amateur astronomers to observe the
giant planet. The estimate was presented at an international workshop
on Jupiter for professional and amateur astronomers organised by
Europlanet 2020 Research Infrastructure at the Observatoire de la Côte
d’Azur in Nice, France.

Meteors impacting Jupiter’s upper atmosphere can create spectacular
fireballs, such as the one observed by amateur astronomers Gerrit
Kernbauer and John McKeon on 17th March 2016. This was the
fourth in a series of fireballs in Jupiter observed serendipitously by
amateur astronomers since June 2010. Groups of amateurs worldwide have
coordinated efforts to obtain improved estimates of the number of small
bodies around Jupiter and how they interact with the planet.

Marc Delcroix, who coordinates a 60-strong group of amateur
astronomers worldwide said, “Dramatic impacts with Jupiter can be
captured with standard amateur equipment and analysed with easy-to-use
software. But to get a good estimate of how often these events occur,
we need observers around the world who are willing to collaborate to
create a programme of more-or-less continuous monitoring of Jupiter. It
takes time and commitment – observations of no impacts are just as
important as detecting a fireball. In 3 years since our programme
started, amateur contributors from Europe, the US and Australia have
analysed the equivalent of more than 56 days of videos – around 53 000
videos — without discovering an impact.

This is a result in itself and,
together with the reports of amateur astronomer John McKeon, has helped
us come up with our preliminary estimate which slightly reduces previous
estimates of the flux of impacting objects in Jupiter. We are now
working to further enhance our software to improve its usability, while
maintaining its simplicity and efficiency, to reach an even wider
participation by amateurs. This should help in refining the impact
estimations for Jupiter, and hopefully discover new impacts.”

Isshi Tabe and Dr Jun-ichi Watanabe, of the Association of Lunar and
Planetary Observers (ALPO) in Japan, set up the Find Flash project
following the observation of an impact flash by four Japanese amateur
astronomers on 20th August 2010.

Tabe explained, “We recognised the importance of impact flashes for
estimating the number of small bodies around Jupiter. We have perhaps
more than 50 Japanese amateur astronomers in our association who take
video images almost every night. We also have around 10 nights per year
observation time on bigger telescopes in public and professional
observatories, which allows us to employ a narrow band methane filter to
detect fireballs in Jupiter’s upper atmosphere more efficiently. We’ve
carried out the observational campaign for three years, but
unfortunately we have never yet detected any impact flashes. We expect
to have an increasing of number of observations over the next few years
and to get valuable data both from bigger and smaller telescopes.
However, in northern hemisphere of Earth, especially in Japan, we can
only get consistently good observational conditions in summer, so it is
important that we work together with other amateur groups around the
world to get more data.”

John McKeon, who observed the St Patrick’s Day impact said,
“Collaboration is extremely important in the amateur astronomer
community. On March 28th I became aware that an amateur astronomer in
Austria, Gerrit Kernbauer, had discovered a possible impact on Jupiter
on March 17th. I remembered I had been filming Jupiter around the same
time, with the intention of illustrating a double moon transit of the
planet. I’d filmed a total of 207 short 55 second movies of the planet
over a period of about 3 and half hours and had processed them to create
a time-lapse animation. When I checked back through my videos, I found
the impact in the second last video I had taken. This secondary
observation helped to confirm the impact event. Having a hand in this
discovery, and the input and support from other amateurs in the analysis
of the event, has changed and improved my imaging process for the
future.”

“The new estimate of 6.5 impacts a year of comparable size objects
lies at the bottom part of our previous estimate of impacts in Jupiter,”
said Ricardo Hueso of the University of the Basque Country and chair of
the workshop’s scientific organising committee. “Constraining this
number is important to improve our expectancies of observing large
impacts in the planet, such as the Shoemaker-Levy impact in 1996 and the
2009 impact. Unfortunately, we are still dealing with the statistics of
a very few number of impacts detected, but plans to improve our
detection methods and perform systematic searches will help us to detect
more of these objects. That will allow us to know more about the
current architecture of the outer Solar System and the role of Jupiter
in protecting the Earth from comparable impacts.”

Since 2005, Europlanet has provided Europe’s planetary science
community with a platform to exchange ideas and personnel, share
research tools, data and facilities, define key science goals for the
future, and engage stakeholders, policy makers and European citizens
with planetary science.

The Europlanet 2020 Research Infrastructure (RI) has received funding
from the European Union’s Horizon 2020 research and innovation
programme under grant agreement No 654208 to provide access to
state-of-the-art research facilities across the European Research Area
and a mechanism to coordinate Europe’s planetary science community. The
project builds on a €2 million Framework 6 Coordination Action and €6
million Framework 7 Research Infrastructure funded by the European
Commission. The Europlanet collegial organisation, linked by a
Memorandum of Understanding (MoU), has a membership of over 70 research
institutes and companies.